Ashworth U.S. Pat. No. 4,097,361 discloses a continuous deep hydrogenation coal liquefaction process using a slurry of powdered coal in a recycle solvent which after hydroextraction passes heavy coal extract into low temperature fluidized bed pyrolysis. The char from the pyrolysis unit is fed to high temperature fluidized bed char gasification.
Manowitz U.S. Pat. No. 3,963,598 discloses a process for hydrogenation of coal by contacting powdered coal with hydrogen in a rotating fluidized bed reactor. The coal residence time in the reactor is limited to less than 5 seconds while the hydrogen contact time is not in excess of 0.2 seconds.
Metrailer et al U.S. Pat. No. 4,204,943 discloses a combination slurry hydroconversion, coking and coke gasification process in which carbonaceous solids having an average particle size of less than 10 microns in diameter are used as a catalyst in the hydroconversion stage.
Conversion of coal to gaseous and liquid products is attended by various difficulties. One problem associated particularly with coals from the eastern United States is that of caking.